Drive an electric power steering motor from an European Opel Corsa C

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vivitern
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Drive an electric power steering motor from an European Opel Corsa C

Post by vivitern » Mon, 27 Nov 2017, 15:59

I want to drive an electric power steering motor from an European Opel Corsa C in a way that I can control the steering of the car programmatically. I have a steering angle sensor which I will to use as rotary encoder for feedback to be able to set a desired steering angle. Unfortunately I do not know what kind of electric motor it is but I suspect a common DC brushed. Can anyone judge from the part number or use scenario on the motor type or do I have to open it to see the internals?

The whole power steering set includes the motor, ECU and torque sensor. In its normal operation, the torque sensor "reads" the torque (on the steering column) that the human driver's hands apply to the steering wheel and the ECU computes how much additional "assistance" will be applied from the power steering. The operation of the set can be seen on this video:https://www.youtube.com/watch?v=DzXxf5iuwDY (Corsa B has identical parts).

A problem with steering is that the torque applied by motor depends not only on the human input but also on vehicle speed - more torque will be needed when vehicle stands still and less when it is moving fast... The ECU probably has a speed/torque map that it uses. I am trying to figure out how to deal with this - I guess the rotary encoder may solve the issue by giving feedback - in case the steering angle would change too slowly, more torque would be needed.

The motor may likely be driven in following two ways:

Reverse engineer the torque sensor. Input "fake" torque readings to the original ECU and let it drive the motor. This method may be easier but may not give precise control of the motor since the ECU will still behave like a black box and will try to map torque via vehicle speed - this may likely be prevented by not inputting speed to the ECU (by disconnecting it from CAN bus) - the ECU would behave consistently then thinking the speed is 0 (or whatever constant).
Directly control the motor with a custom driver like BA6235F(datasheet:http://www.kynix.com/uploadfiles/pdf/BA6235.pdf). This may be harder but will give full control over the motor. Rotary encoder may be used to deal with the speed/torque dependency.
The motor looks like this (part number - GM/NSK 1407140):

Image

Image

This is the whole power steering set (motor, ECU and torque sensor):

Image

My ECU part number is 13136672:

Image

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Richo
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Re: Drive an electric power steering motor from an European Opel Corsa C

Post by Richo » Tue, 28 Nov 2017, 12:18

vivitern wrote:
Mon, 27 Nov 2017, 15:59
Can anyone judge from the part number or use scenario on the motor type or do I have to open it to see the internals?
2-wires (Red and black) means it is, as you say, a regular brushed DC motor.
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Richo
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Re: Drive an electric power steering motor from an European Opel Corsa C

Post by Richo » Tue, 28 Nov 2017, 12:25

vivitern wrote:
Mon, 27 Nov 2017, 15:59
The whole power steering set includes the motor, ECU and torque sensor.
Nah I doubt it's a torque sensor.
Just a simple hall(position) sensor.

Box is more likely a PID controller.
When you turn the steering wheel and the car is stationary the current will be higher giving a higher response through the PID to compensate.
When you turn the steering wheel and you are travelling the current will be lower giving a damped response through the PID.

Interesting parts you have tho...
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Re: Drive an electric power steering motor from an European Opel Corsa C

Post by Richo » Tue, 28 Nov 2017, 12:33

vivitern wrote:
Mon, 27 Nov 2017, 15:59

The motor may likely be driven in following two ways:

Reverse engineer the torque sensor. Input "fake" torque readings to the original ECU and let it drive the motor. This method may be easier but may not give precise control of the motor since the ECU will still behave like a black box and will try to map torque via vehicle speed - this may likely be prevented by not inputting speed to the ECU (by disconnecting it from CAN bus) - the ECU would behave consistently then thinking the speed is 0 (or whatever constant).

Directly control the motor with a custom driver like BA6235F(datasheet:http://www.kynix.com/uploadfiles/pdf/BA6235.pdf). This may be harder but will give full control over the motor. Rotary encoder may be used to deal with the speed/torque dependency.
The motor looks like this (part number - GM/NSK 1407140):
Careful with kynix - grey market parts etc...
BA6235F is interesting but is old and probably not suited for this application.

I'd suggest give to to some uni student and let them do it as a final project.
You could probably get away with some ARM eval module and a H-Bridge.
Let them fiddle with the PID constants etc...
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Re: Drive an electric power steering motor from an European Opel Corsa C

Post by Richo » Tue, 28 Nov 2017, 12:38

Oh hi Vivitern and welcome to the AEVA 8-)
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Richo
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Re: Drive an electric power steering motor from an European Opel Corsa C

Post by Richo » Tue, 28 Nov 2017, 12:45

Richo wrote:
Tue, 28 Nov 2017, 12:25
Nah I doubt it's a torque sensor.
Just a simple hall(position) sensor.
Even if it is a torque sensor the base electronics doesn't really change much.

http://www.jurnalteknologi.utm.my/index ... /view/3464


What do you plan to do with this equipment?
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Re: Drive an electric power steering motor from an European Opel Corsa C

Post by Richo » Tue, 28 Nov 2017, 12:51

I see there are aftermarket retrofit kits:
https://www.ultimatepowersteering.com.a ... ng-epas-1/

$1,600+ :shock:
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